Ab initio calculations of the properties of defective CsSnCl₃: The role of anion-cation pair defect

In this study, first principles calculations based on density functional theory (DFT) was used to simulate the geometric structures, electronic, optical, and mechanical properties, of inorganic CsSnCl₃ perovskites with and without an anion-cation pair defect (Sn and Cl vacancy). The data establishes that the introduction of vacancies induce a trap state which narrows the band gap. The formation of the observed trap states can be ascribed to the orbital hybridization of the Sn atoms near the vacancy site. In addition, the defective CsSnCl₃ perovskite showed better light absorption in the visible region than its pristine counterpart owing to a reduced band gap. The mechanical properties predicted the pristine and defective CsSnCl₃ perovskites to be mechanically stable.